The best option depends on the problem you want to solve. Draught proofing addresses unwanted air leakage; secondary glazing adds an internal glazing layer; double glazing changes the glazing within the window. Assess condition, ventilation and heritage constraints before choosing a system.
Start with the room, not a product name
Describe when the room feels uncomfortable. Is there a noticeable draught beside the meeting rails, a cold sensation near the glass, traffic noise, or moisture on the window? Record whether the symptoms vary with wind, rain or overnight heating. Several causes may exist together, so one product should not be assumed to solve them all.
How do the choices differ?
- Draught proofing: ask which gaps will be treated, how the sashes will move afterwards and how necessary room ventilation will be maintained.
- Secondary glazing: ask where the internal unit will sit and how it will open for ventilation, cleaning and maintenance. Check its relationship with shutters, handles and blinds.
- Double glazing: ask whether the existing sashes can accept the proposed unit, whether new sashes are needed, and how glass weight, glazing bars and balance will be addressed.
HES describes draught proofing, shutters and secondary glazing as options for reducing heat loss from traditional windows. Read its heat-loss guidance for the conservation context.
Should draught proofing and secondary glazing always be combined?
No. The room ventilation and the cavity between the old and new glazing need to be considered together. Scottish Government guidance on traditional building conversions cautions against draughtproofing the original window where secondary glazing is used, to maintain a ventilated cavity and reduce condensation risk. Ask the designer to specify an appropriate arrangement for your particular system; do not automatically seal every gap. See the condensation guidance.
What evidence should you request?
Ask for performance information for the actual proposed product and installation. A laboratory figure for glass alone is not a promise about the whole room, the complete installed window or your fuel bill. If noise is your main concern, ask what evidence supports the proposed acoustic performance. Avoid choosing solely from percentage-saving claims without their test conditions.
Can you retain original features?
Take photographs of the glass, shutters and internal surrounds before the survey. Ask to see a section drawing or sample showing the proposed sightlines and fixing position. For a listed property or one in a conservation area, confirm relevant permissions with the planning authority before ordering.
Related advice and services
- Draught proofing service
- Secondary glazing
- Heritage slimline double glazing
- Timber shutter restoration
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Discuss your windows
For a property in Stirling or Central Scotland, contact The Sash and Case Window Company with photographs and a description of the problem. An inspection can establish which work is appropriate for your windows.